During the last decade there has been considerable interest in the electrochemical field in use of cation exchange membranes as separators in electrochemical cells particularly in the industrial chlor-alkali field and in redox batteries. The cation exchange membranes are perfluorinated and non-fluorinated ionomer membranes containing sulfonate and/or carboxylic groups in the resin, the perfluorinated species being discussed in an article entitled "ELECTROLYTIC CELL MEMBRANE DEVELOPMENT SURGES" by Stinson in the Mar. 15, 1982 issue of the C & E News, the disclosure of which is incorporated herein by reference. These materials are permeable to cations but provide an effective barrier to anions and are particularly attractive in the electrochemical battery field because they are highly conducting, highly selective in the materials which they pass and have suitable mechanical properties. An additional important characteristic in the electrochemical cells is that these membranes are chemically and thermally stable at cell operating conditions.